This invention relates generally to the field of ride control systems and, in particular, to an apparatus and method for automatically adjusting the ride of a loader type vehicle.
When a loader vehicle such as, for example, a wheel loader, a backhoe loader, a skid steer loader or forklift machine travels across bumps or other obstacles, the resultant energy is transferred to the vehicle which may cause it to bounce. This may cause the spillage of an object or material carried by the loader vehicle. Moreover, excessive bouncing may result in an excessive amount of wear and tear on the loader vehicle, and an unacceptably harsh ride for the operator.
Attempts have been made to provide improved ride performance for these types of loader vehicles by using the weight of the load carrying structure of the vehicle to dampen the ride. In particular, these ride control systems typically route the hydraulic pressure generated by the load carrying structure to a hydraulic accumulator. When the loader vehicle travels over a bump, for example, the accumulator absorbs the increased hydraulic pressure thereby improving the ride of the vehicle. However, these accumulators are typically sized with an initial gas charge that is selected to provide an optimum ride for only one load. Moreover, the gas charge in these accumulators cannot be automatically adjusted to a level that is optimum for the specific load being carried. As a result, only one specific load will result in the optimum performance of the ride control system. Although these accumulators may provide some benefit when loads are higher or lower than the optimum, they do not automatically adjust to provide optimum ride performance for varying loads.
Accordingly, it would be desirable to have an apparatus and method for automatically controlling the ride of loader type vehicles that overcomes the disadvantages described above.
One aspect of the invention provides an apparatus for adjusting the ride of a load carrying vehicle. The apparatus includes a sensor, a controller, and an adjustable accumulator assembly. The sensor measures a load on a load holding hydraulic circuit. The controller is operatively connected to the adjustable accumulator assembly. The controller is capable of adjusting the pressure in the accumulator in response to the load measured by the sensor.
Another aspect of the invention provides a method for adjusting the ride of a loader vehicle. An accumulator assembly including a first accumulator operatively connected to a second accumulator by a valve is provided. The first and second accumulators each include a gas chamber, a fluid chamber, and a piston that separates that gas chamber and the fluid chamber. A hydraulic load holding circuit is operatively connected to the second accumulator. Pressure on the hydraulic load holding circuit is sensed and a load on the hydraulic load holding circuit is determined from the sensed pressure. A desired pressure for the gas chamber of the second accumulator is determined. A desired precharge number of gas molecules for the gas chamber of the second accumulator is also determined. The hydraulic load holding circuit is isolated from the fluid chamber of the second accumulator. The valve is opened. The position of the piston of the first accumulator and the position of the piston of the second accumulator are determined. A desired position of the piston of the first accumulator that is optimum for the load on the hydraulic load holding circuit is determined. The position of the piston of the first accumulator is adjusted until the desired position is reached. The valve is closed, and the hydraulic load holding circuit is connected to the fluid chamber of the second accumulator. The position of the piston of the first accumulator and the position of the piston of the second accumulator may preferably be monitored.
Another aspect of the invention provides a method for adjusting the ride of a loader vehicle. An accumulator assembly including a first accumulator operatively connected to a second accumulator by a valve is provided. The first and second accumulators each include a gas chamber, a fluid chamber, and a piston that separates that gas chamber and the fluid chamber, a hydraulic load holding circuit operatively connected to the second accumulator. Pressure on the hydraulic load holding circuit is sensed and a load on the hydraulic load holding circuit is determined from the sensed pressure. A desired precharge pressure for the gas chamber of the second accumulator is determined. A desired number of gas molecules for the gas chamber of the second accumulator is then determined. The hydraulic load holding circuit is isolated from the fluid chamber of the second accumulator. The valve is opened, and the position of the piston of the first accumulator is determined. The pressure in the gas chamber of the second accumulator is determined. The position of the piston of the second accumulator is also determined. A desired position of the piston of the first accumulator that is optimum for the load on the hydraulic load holding circuit is also determined.
The position of the piston of the first accumulator is adjusted until the desired position is reached. The valve is closed and the hydraulic load holding circuit is connected to the fluid chamber of the second accumulator.
Another aspect of the invention provides a method for adjusting the ride of a loader vehicle. An accumulator assembly including a first accumulator operatively connected to a second accumulator by a valve is provided. The first and second accumulators each include a gas chamber, a fluid chamber, and a piston that separates that gas chamber and the fluid chamber. A hydraulic load holding circuit is operatively connected to the second accumulator. Pressure on a hydraulic load holding circuit is sensed and a load on the hydraulic load holding circuit is determined from the sensed pressure. A desired precharge pressure for the gas chamber of the second accumulator is determined. The hydraulic load holding circuit is isolated from the fluid chamber of the second accumulator. The valve is opened, and the position of the piston of the first accumulator is adjusted until the desired position is reached. The valve is closed and the hydraulic load holding circuit is connected to the fluid chamber of the second accumulator. Fluid is prevented from flowing between the fluid chamber of the second accumulator and the tank. The pressure in the gas chamber of the second accumulator may preferably be monitored.
The invention provides the foregoing and other features, and the advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the invention and do not limit the scope of the invention, which is defined by the appended claims and equivalents thereof.